Efficient cryopreservation protocol enables accessibility of a broad range of ammonia-oxidizing bacteria for the scientific community.

Long-term storage of the fastidious ammonia-oxidizing bacteria has proven difficult, which limits their public availability and results in a loss of cultured biodiversity. To enable their accessibility to the scientific community, an effective protocol for cryopreservation of ammonia-oxidizing cultures at -80 °C and in liquid nitrogen was developed. Long-term storage could be achieved using 5% DMSO as cryoprotectant, preferably in a cryoprotective preservation medium containing tenfold-diluted trypticase soy broth and 1% trehalose. As such, successful activity and growth recovery was observed for a diverse set of ammonia-oxidizing cultures.